1. Field of the Invention
The present invention relates to a conversion adaptor apparatus and an interchangeable lens system.
2. Description of the Related Art
In response to the desire to decrease the size and weight of digital single reflex lens cameras, in recent years a new type of single lens reflex camera that differs from the conventional single lens reflex camera has been proposed. The new type of single lens reflex camera is not provided with a quick return mirror for guiding the imaging light flux to a viewfinder, and the flange back is shorter than that of a conventional camera. The new type of interchangeable lenses having a short flange back that is compatible with this new type of camera has been proposed. However, these new type of interchangeable lenses cannot easily handle a variety of photographic conditions because there are few models. Therefore, there are cases in which it is desirable to use in the new type of camera the conventional type of interchangeable lenses that have already been introduced to the market and for which there are ample models and quantities. Thus, a conversion adapter for connecting the conventional type of interchangeable lenses with the new type of camera body is necessary. The functions required of this conversion adapter generally include matching the differing mounting profiles of the lenses and the camera body, matching the differing flange backs of the lenses and the camera body, and not hindering the communication system between the lenses and the camera body.
In order to enable communication, which is a necessary function of a conversion adaptor, between the camera body and the interchangeable lens, communication contacts are provided on the conversion adaptor. A conversion adaptor has been proposed in which the positions of the communication contacts connecting the camera body side and the communication contacts connecting the interchangeable lens side of the conversion adaptor are provided at positions around the camera optical axis that are identical. In this conversion adaptor, for example, a conducting member is provided that electrically connects two corresponding connection contacts among the communication contacts that connect to the camera body side (camera body side communication contacts) and the communication contacts connected to the interchangeable lens (lens side communication contacts).
Note that Japanese Patent Laid-Open No. H4-273671, discloses a conversion adaptor in an interchangeable lens system that controls a first lens unit by communicating a control signal having a first signal profile output from the camera body to a first lens unit. This conversion adaptor apparatus enables a second lens unit, which is controlled by control information having a second signal profile that is different from the first signal profile, to connect to the camera body.
However, when the flange back of the camera body of the new type of camera described above and the flange back of the conventional type of lens are close, the conversion adaptor must be made thin. When the conversion adaptor is made thin, providing the camera body side communication contacts and the lens side communication contacts of the conversion adaptor at positions around the camera optical axis that are identical is difficult because they are spatially too close. In addition, in the case in which the camera body side communication contacts and the lens side communication contacts are close to the position of the camera optical axis, the layout of the conducting member that provides electrical conduction between these communication contacts becomes difficult. In addition, the assembly operability of the camera body side communication contacts, the lens side communication contacts, and the conducting member deteriorates.